A hot section component of a combustion turbine is routinely subjected to rigorous mechanical loading conditions at high temperatures. A thermal barrier coating is typically formed on such a substrate of the combustion turbine component to insulate it from such large and prolonged heat loads.
The thermal barrier coating insulates the combustion turbine component substrate by using thermally insulating materials that can sustain an appreciable temperature difference between the substrate of the combustion turbine component and the thermal barrier coating surface. In doing so, the thermal barrier coating can allow for higher operating temperatures while limiting the thermal exposure of the combustion turbine component substrate, extending part life by reducing thermal fatigue.
Such a thermal barrier coating is typically formed on a bond coating, the bond coating being formed on the combustion turbine component substrate. The bond coating creates a bond between the thermal barrier coating and the combustion turbine component substrate.
As disclosed in U.S. Pat. No. 7,087,266 to Darolia et al., such a bond coating may be formed from a MCrAlY alloy, with M being selected from the group comprising Fe, Co, Ni, and mixtures thereof. This bond coating may be effective at maintaining the bond between the thermal barrier coating and the substrate up to about 1200° C. However, at temperatures greater than 1200° C., such a MCrAlY bond coating may become brittle and spallation (delamination and ejection) of the thermal barrier coating from the substrate may occur. Such spallation may lead to undesirable component wear and/or failure.
Some efforts at enhancing bond coating performance have focused on tailoring the composition of the combustion turbine component substrate itself to provide better compatibility with the bond coating and thus better bond coating performance. U.S. Pat. Pub. 2007/0202003 to Arrell et al., for example, discloses a variety of nickel based superalloy compositions with such an enhanced bond coating compatibility. However, in some applications, enhanced bond coating performance with combustion turbine component substrates formed from other alloy compositions may be desirable.
U.S. Pat. No. 6,485,844 to Strangman et al. discloses a bond coating for nickel based superalloy articles that is capable of withstanding high temperatures. The bond coating has a thickness of 0.4 μm to 1.2 μm and comprises, by percentage of weight, 5%-25% platinum, 5-16% aluminum, with a balance of nickel.
U.S. Pat. No. 7,354,651 to Hazel et al. discloses a silicide-containing bond coating for a silicon-containing combustion turbine component substrate. The bond coating is corrosion resistant and may withstand high temperatures. However, in some applications, a combustion turbine component substrate that does not contain silicon may be desirable.
Bond coatings formed from other compositions and having different properties, however, may be desirable. Moreover, bond coatings with increased oxidation resistance, increased thermal shock resistance, and high temperature particle stability are also desirable.